Furnace arch



March 13, 1956 K. H. KAUTH EFAL FURNACE ARCH Filed Sept. 23, 1952 FIG. I

KARL CHRISTIAN 1N VENTOR RUCHHAU SEN ATTORNEYS United States Patent FURNACE ARCH Kan Hermann Knuth and Christian Bruchhausen, Duisburg, Germany, assignors to Didier-Werke A. G., Wiesbaden, Germany, a German firm Application September '23, 1952, Serial No. 311,012 9 cnim's. (cl. 11 01.99)

The present invention relates to a furnace arch and,

more particularly, to an arch for a Siemens-Martin furna'ce. It is a disadvantage of arch-shaped roofs of Siemens- Martin furnaces when the arch is constructed throughout of the same constructional material, that they are subject to greater wear, especially because of fusion or melting oil, at the better parts of the furnace than at those which are not quite so hot. Thus, arches which are constructed throughout of silica brick are considerably worn off in a relatively short time at the points adjacent the supporting wall, while the parts at the center of the arch undergo only slight wear. A similar phenomenon is observed with arches which are built throughout of magnesite brick, chromite brick, etc., the melting points of which are higher than that of silica brick. The sole effect of the higher melting points is to retard the wear somewhat as compared to silica brick.

This uneven wear is prejudicial to the static strength of the arch and results in a premature deterioration of the latter. Attempts have been made to eliminate the said disadvantage by making the arch of refractory brick with a very high melting point at the hotter portions and of refractory brick with a lower melting point at the less hot portions, in an effort thus to realize as uniform a wear as possible throughout the arch. In addition to thus achieving a longer life of the arch, the replacement of high melting point refractory brick by the cheaper lower melting point refractory brick at the less hot portions of the furnace represented an economy, since the high melting point brick are much more expensive than the lower melting point brick. V p

However, attempts of this character, for example with chromite-mag'nesite brick at the hotter spots and silica b'rick at the less hot spots, brought only unfavorable results. The thus-constructed arches broke down without apparent cause in a short time, although the usual wear and teareven at separated"spots-was not visually recogniz'able.

A primary object of the present invention is to embody an arch construction of the aforementioned type which is free of the precedingly described disadvantage and which has a long life.

This object is realized according to the present invention, briefly stated, by the expedient (a) of preventing the formation, at a temperature below the operating temperature, of a eutectic layer at the contact surfaces of the two different types of brick by the interposition therebetween of a material which does not react with the adjacent brick at all, orv (b) of interposing a material between the two types of brick, which material reacts very slowly with the latter and eventually forms a eutectic layer, the melting point of which is not appreciably lower than the melting points of the acid and basic arch brick, and (c) regulating or entirely eliminating arch pressure by suspending the bricks constituting the arch.

At the points or surfaces of contact between the acid and basic brick involved in an arch construction accord- 2,737,912 Patented Mar. 13, 1956 2 ing to this invention, which brick may for example be silica brick on the one hand and chromite-magnesite brick on the other hand, there are interposed bricks which may be of the same configuration as the other bricks constituting the arch but which do not enter into reaction with the acid (silica) brick or with the basic (chromite-magnesite) brick at the temperature of operation of the furnace. Such non-reactive brick are for example quartzite brick containing not less than 97% SiOz. Non-reactive brick of thischaracter do not react with adjacent brick (acid or basic) at all or, if areaction does occur, it is so slight that no formation of a prejudicial eutectic layer having a melting point which is considerably lower than that of the silica brick, takes place.

The non-reactive layer need not be constituted by preformed brick but may just as well be made up from a bulk mass, as for example a mass of mortar. Such mass is preferably of the same composition as the previously described non-reactive brick. Other suitable compositions, than those aforementioned by way of example, may also be employed.

The invention positively excludes the possibility of the formation of a eutectic layer of low melting point or at least obviates any unfavorable effect of such layer by suppressing such formation beyond a minimum amount and by preventing the lowering of the melting point to a dangerous low point.

The positive exclusion of the possibility of eutectic formation between adjacent bricks of different composition obviates the weaknesses inherent in such eutectic. Among other things, a layer of such eutectic constitutes a point of weakness in the arch construction because the eutectic cannot withstand the arch pressure. The result is aims in static strength of the arch which is then subject to rapid deterioration and even to collapse. V

A further enhancement of the stability of the mixed (acid brick and basic brick) arch is realized by the suspension mounting of the brick. 7 It is of course per se known to mount arch brick in suspendedform, individually or groupwise. 7 However, such constructions have hither to always involved brick of one and the same typeor coiniposition, for example only silica brick or only chromitemagnesite brick. In a mixed arch, involvingforeXample chromite-magnesite brick and silica brick, the suspension mounting not only eliminates arch stress due tothe weight of the brick themselves, but the prejudicial 'he'atand-high-pressure effect which occurs at the pointsof contact between the different types of brick in a mixed brick arch is converted into what maybe termed pressureles-s heat. This retards or entirely eliminates the formation of a eutectic. Particularly where a non-r eact ive intermediate layer is incorporated does the obviation of heating under pressure eliminate the 'formationof even a slight eutectic layer with a dangerous low melting point. Likewise, the suspension mounting of the arch br'ickals'o prevents a crushing, due to pressure influences, of the less pressure-resistant brick at the points of contact ofth'e two aforesaid types of brick.

it is preferable to suspendingly mount the arch brick directly onto the beam construction. To this end, use may for example be made of an i-beam of a "configuration corresponding to that of the arch and positioned on the upper side of the arch. The arch brick themselves are advantageously formed with a head-piece provided with a slot in which the beam flange engages. instead of an I-beam, which may be of cast iron, any other suitably configured beam may be employed.

These brick-carrying beams are, in turn, advantageously suspended from and/or supported by overlying carrier members. The rigid brick-carrying beams allows no lifting of the cover brick; all arch brick remain in their intended plane. The swelling or shrinking of the arch brick as well as the thermal expansion thereof takes place in the plane of the arch; a deviation in the upward or downward direction is impossible. The intermediate space between the individual arch brick when the latter are laid is adjusted in accordance with the known behavior of the brick, taking swelling and shrinking into account. In this way, arch pressuresparticularly between the arch bricks proper and the intermediate bricks-which may give rise to the formation of eutectic layers are wholly eliminated.

On the accompanying sheet of drawings, wherein several presently-preferred embodiments of the invention are illustrated by way of example:

Fig. 1 is a diagrammatic representation of a longitudinal section through one embodiment of arch construction according to the invention,

Fig. 2 is a diagrammatic representation of a transverse section through a second embodiment of arch construction according to the invention,

Fig. 3 is a transverse section showing a suspended type of arch construction according to the invention, and also showing means for pr venting outward bulge of the arch, and

Fig. 4 is a longitudinal section taken along line 44 of Fig. 3.

The arch, shown in Fig. 1 in longitudinal section, is in transverse section (not shown) arcuate after the manner illustrated in Figs. 2 and 3. Similarly, the arch shown in Fig. 2 in transverse section is, in longitudinal section (not shown) of the general configuration of the arch proper illustrated in Figs. 1 and 4. The arch of each of Figs. 1 and 2 will be understood to be supported in the essentially conventional way by the usual supporting walls, generally after the manner shown in Fig. 3 (see supports 8). The arch of each of the figures of drawing may for example be arranged above the hearth of a Siemens- Martin furnace.

The arch construction according to Fig. 1, viewed in the longitudinal direction, may advantageously consist, at its two ends 1, of basic (chromite-magnesite) bricks and at its middle portion 2 of acid (silica) bricks. At each surface of contact between basic brick and acid brick, there is interposed a layer 3 of a material which is essentially inert toward the two aforesaid (acid and basic) types of brick. The layers 3 may for example be made of preformed quartzite brick containing not less than 97% SiOz. In transverse section, the layers 3 will of course be arched to conform to the transverse configuration of the arch.

The arch construction according to Fig. 2, viewed in the transverse direction, involves an alternative arrangement according to which the portions 4 of the arch which rest upon the supporting walls consist of basic (chromitemagnesite) bricks and the central portion 5, at the top of the arch, consists of acid (silica) bricks. In this embodiment, the layers 6 of non-reactive refractory material which are severally interposed, as shown, between contacting surfaces of the said arch portions 4 and 5, extend in the longitudinal direction of the arch.

As hereinbefore indicated, the invention is also applicable to constructions wherein the constituent bricksacid, basic and interposed non-reactive brick-are suspendingly mounted on suitable supports. This embodiment of the invention is illustrated in Figs. 3 and 4, and comprises I-beams 7 which (Fig. 3) are curved to correspond to the shape of the arch and are arranged on the upper side of the latter. The individual bricks 4, 5, 6 are provided with head pieces 9 which are slotted, as

at 10 (Fig. 4) to provide slots for the reception of the lower flange portions of I-beams 7.

I-beams 7 are, in turn, suspended from EI-shaped supporting beams 11, a rigid connection being provided between beams 11 and beams 7 in any suitable and conventional manner, as by means of bolts, rivets or weld joints.

Carrier beams 11 are suspended from the supporting frame 13 by means of threaded carrier rods 12. Nuts 14, mounted on rods 12, provide means for adjusting the beams 11 to the desired position. Nuts 15 which are drawn against the underside of supporting frame 13 after beams 11 have been adjusted to the desired height, prevent undesired upward bulging of the arch. The latter proper comprises brick 4, 5 and 6 as in the embodiment of 2.

Having thus disclosed the invention, what is claimed is:

l. A furnace arch, particularly for a Siemens-Martin furnace, said arch comprising refractory bricks of different compositions and melting points and including acid bricks and basic bricks, which bricks when in contact at elevated temperature react at the surfaces of contact between acid bricks and basic bricks to form intermediate eutectic layers of low melting point, and a layer of quartzite interposed between adjacent different brick surfaces, said quartzite being essentially non reactive with said different bricks under the operating temperature conditions of said furnace.

2. A furnace arch according to claim 1, wherein the said intermediate layers consist of pre-formed bricks of the said quartzite.

3. A furnace arch according to claim 1, wherein the said layer is in the form of bricks of the said quartzite, and means including a superstructure for suspendingly supporting all said bricks.

4. A construction according to claim 1, wherein the said layer is of quartzite with not less than 97% SiOz.

5. A construction according to claim 1, wherein the said layer consists of quartzite bricks with not less than 97% SiOz.

6. A furnace arch, particularly for Siemens-Martin furnaces, consisting primarily of silica bricks and having bricks of basic reaction interposed at the parts of the furnace arch which are hottest when the furnace is in operation, and a layer of quartzite, which is essentially non-reactive with the silica bricks and the basic bricks under the operating temperature conditions of said furnace, inteiposed therebetween.

7. A construction according to claim 6, wherein the said layer is of quartzite with not less than 97 SiOz.

8. A furnace arch according to claim 6, wherein the said layer is in the form of bricks of the said quartzite, and means including a superstructure for suspendingly supporting all said bricks.

9. A construction according to claim 6, wherein the said said layer consists of quartzite bricks with not less than 97% SiOz.

References Cited in the file of this patent UNITED STATES PATENTS 1,191,271 Bow July 18, 1916 1,477,811 Crawford Dec. 18, 1923 1,686,387 Loftus Oct. 2, 1928 1,714,506 Heuer May 28, 1929 2,085,837 Thomas July 6, 1937 2,158,759 Morlock May 16, 1939 2,236,920 Robertson Apr. 1, 1941 2,304,170 Heuer Dec. 8, 1942 

1. A FURNACE ARCH, PARTICULARLY FOR A SIEMENS-MARTIN FURNACE, SAID ARCH COMPRISING REFRACTORY BRICKS OF DIFFERENT COMPOSITIONS AND MELTING POINTS AND INCLUDING ACID BRICKS AND BASIC BRICKS, WHICH BRICKS WHEN IN CONTACT AT ELEVATED TEMPERATURE REACT AT THE SURFACES OF CONTACT BETWEEN ACID BRICKS AND BASIC BRICKS TO FORM INTERMEDIATE EUTECTIC LAYERS OF LOW MELTING POINT, AND A LAYER OF QUARTZITE INTERPOSED BETWEEN ADJACENT DIFFERENT BRICK SURFACES, SAID QUARTZITE BEING ESSENTIALLY NON-REACTIVE WITH SAID DIFFERENT BRICKS UNDER THE OPERATING TEMPERATURE CONDITIONS OF SAID FURNACE. 